Angiotensin II / Aldosterone function
Angiotensin II has direct effect on controlling peripheral circulation and also glomerular filtration through
afferent arteriole. Also stimulates production of vasopressin from the hypothalamus. Indirectly Angiotensin
II exerts influences things that vasopressin does. That allows it to have more broad reaching effect.t
Angiotensin II activates adrenal cortex to produce aldosterone which produces significant effects on kidney.
How Potassium ions are regulated?
1. K+ is filtered
2. K+ also Secreted ***
3.K+ is NOT reabsorbed
Potassium ions are in the low concentrations.
What happens once the K+ cells is inside epithelial cells?
Doesn’t stay there forever, the potassium channels allow it to leave. The potassium ions can only go out one
way. When the potassium channels located on the luminal side.
The action of Sodium-Potassium pump causes you to secrete potassium ions, while you are reabsorbing Na
ions. You cannot separate them, this process of secretion, is regulated .
Why is it important to regulate K+ levels?
Since K+ is important for establishing resting membrane potential, implications for excitable cells. When K+
levels get too high in the ECF the cells can depolarize. That can cause cells to be less capable of responding
to capable signals.
The K+ cells have to be within a moderate range so the cells function properly
Aldosterone Production & Action
Aldosterone from the adrenal cortex (steroid hormone which means its lipid soluable) , it freely diffuses across
plasma membrane. It has receptors in cytoplasm of the cell, and it binds to it.
Steriod hormone receptors when bound by the ligand(aldosterone), they act as transcription factors. They
move from cytoplasm to nuclus and binds to target DNA sequence that are specific for steroid hormone. It will
cause increased transcription of those targets, and from that we get translation of new proteins.
This is a process that takes a little while to take an effect. It takes several hours for accumulation of these
proteins. The proteins that it is targeting within the kidney epithelial cells are channels (Na and K it makes
both of them).. These channels when made are then inserted in the Luminal membrane.
Aldosterone: targeted to enhance the transport of Na & K+.
Upon the presence of Aldosterone, there will be more secretion of K+ ions since the capacity is increased to
transfer it, and also reabsorption of the Na ions will be increased.
Water molecules tend to follow Na ions, when we are reabsorbing more Na+ then there is also water molecules reabsorption increase.
Aldosterone can be triggered by couple of hormones,
Angiotensin II stimulates the adrenal cortical cells to produce Aldosterone and that occurs, via the stimulus
which increases the Angiotensin II.
Increasing Renin & Angiotensin II will produce Aldosterone
Low MAP, Reductions in Total Na ions, Reductions in ECF,
**THE TWO IONS ARE ALWAYS BEING MOVED IN OPPOSITE DIRECTIONS THROUGH ACTIONS OF
K+ does have the capacity to regulate MAP.
Tumours within the adrenal cortex that cause hyper secretion of Aldosterone, these individuals are getting rid
of too much K+ , so they have problems maintain a steady levels . They wil be absorbing too much Na & water
causing their blood pressure to increase.
Response to low sodium
Aldosterone helps you deal with it.
Sodium ions are always linked with water, because Na is the most predominant ion in the ECF and its main
thing that controls water balance in the ECF. So whenever Na levels are changed, the fluid vols are changed
and have an effect on blood pressure.
Direct Effect on Glomerular Filtration Rate because reducing the hydrostatic pressure witin the glomerulus.
Lower filteration = less Na ions entering filterate, less that will eventually be excreted.
Direct effect that affects Na levels will be also utilizing Aldosterone via production of Renin and Angio- tension
This will help absorb more Sodium
**THE SYSTEM IS GOING TO USE THESE VARYING HORMONES that have exert influence in a variety of
different places in your body to manage predominately manage ECF volume and keep th